In 1599 Sagredo apologized to Galileo for failure to secure a salary increase for him from the university, although he had used his influential family connections to argue his case.

[7]: 42  In 1602 Galileo drew up a horoscope for Sagredo, which describes him as "blandum, laetum, hilarem, beneficum, pacificum, sociabilem, pronum ad voluptates, Dei amatorem, laborum impatientem" (kind, happy, merry, beneficient, pacific, sociable pleasure-loving, a lover of God, and impatient of troubles).

[9]: 33  One of the hopes that resulted from Gilbert's work was that an all-encompassing mapping of global magnetic declination could be used to solve the problem of calculating longitude.

Galileo learned how to arm these magnets and the most powerful - known as Rodomonte - was offered for sale to Ferdinando I de' Medici, Grand Duke of Tuscany and to Emperor Rudolf II.

[9]: 36 In April 1606 escalating disputes between Venice and the Vatican led Pope Paul V to decree the Venetian Interdict and Doge Leonardo Donato to expel the Jesuits from the Republic.

Pretending to be a wealthy widow, Cecilia Contarini, Sagredo wrote to the rector asking for advice on how to get around the Venetian laws which prevented her from leaving the Jesuits a large bequest.

[11] That his underlying attitude towards the Jesuits was unchanged is shown by a letter he sent to Sarpi on 30 April 1609 describing how the world was gradually falling prey to them, especially in eastern India and Japan.

[12] In this capacity he was visited by one Xwāje Ṣafar, an Armenian merchant traveling to Venice on behalf of Shah Abbas, who carried with him the correspondence from the Carmelites of Isfahan.

Another file contained details of the negotiations between Abbas and Philip for the drafting of an anti-Ottoman treaty, which would have had an impact on Venetian access to Persian silk.

Shah Abbas appointed him 'General Procurator' for Persia in the Venetian Republic in 1611[12][13] and in 1613 he began a two-year service as one of the Cinque Savi alla Mercanzia, Venice's Board of Trade.

Their correspondence from 1612 to 1620 covers various topics: astronomy, optics and lens production, thermoscopy, cartography, time zones, tide theory, hydrostatics and magnetism, but also dogs, painting, literature, wine and women.

Sagredo added a scale to Galileo's thermoscope to enable the quantitative measurement of temperature,[14] and produced more convenient portable thermometers.